Re: C2014Q2
Posted: Sat Jan 17, 2015 7:58 pm
Hi all:
Leave a graphic on 16 January. I think all we do a good job.
Friendly, Joan.
Leave a graphic on 16 January. I think all we do a good job.
Friendly, Joan.
Page 4 of 6
Re: C2014Q2
Posted: Sat Jan 17, 2015 10:00 pm
Félicitations à tous pour vos profils: Umberto
Re: C2014Q2
Posted: Sun Jan 18, 2015 7:59 pm
After Robin and Martin highlighting about comet radial velocity, I tried to compare some spectra in database, finding a significant redshifting after a few days.
Left panel shows two observations close together (around comet approach to Earth) so there was a small Vrad difference (~2 Km/s from ephemeris). Furthermore one of the two spectrum has not an high resolution (R~5000).
On the right, two hi-res spectra (R=11000 and 15000) show very well the Vrad difference between Jan 7 and 13 (~13 Km/s from ephemeris and ~12 Km/s measured averaging some lines). On Jan 13 the comet was moving away from us, then the spectrum redshifted by about 0.26A.
A plot of comet distance from Earth and radial velocity ("delta-dot" of JPL/HORIZONS ephemeris):
During the Earth fly-by, Vrad had the maximum negative value on Nov, 28 (-36.9 Km/s) and will become positive maximum on next Feb, 10 (33.8 Km/s).
Paolo
Left panel shows two observations close together (around comet approach to Earth) so there was a small Vrad difference (~2 Km/s from ephemeris). Furthermore one of the two spectrum has not an high resolution (R~5000).
On the right, two hi-res spectra (R=11000 and 15000) show very well the Vrad difference between Jan 7 and 13 (~13 Km/s from ephemeris and ~12 Km/s measured averaging some lines). On Jan 13 the comet was moving away from us, then the spectrum redshifted by about 0.26A.
A plot of comet distance from Earth and radial velocity ("delta-dot" of JPL/HORIZONS ephemeris):
During the Earth fly-by, Vrad had the maximum negative value on Nov, 28 (-36.9 Km/s) and will become positive maximum on next Feb, 10 (33.8 Km/s).
Paolo
Re: C2014Q2
Posted: Sun Jan 18, 2015 8:53 pm
Good work Paolo.
Saluti tanti, Joan.
Saluti tanti, Joan.
Spectroscopy of comets: presentation from Nicolas Biver
Posted: Mon Jan 19, 2015 12:53 pm
Hello,
A very good resources from Nicolas Biver on comet analysis (in french but I suspect it can be understood by all):
http://www.astrosurf.com/jpmasviel/unpe ... comete.pdf
Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/
A very good resources from Nicolas Biver on comet analysis (in french but I suspect it can be understood by all):
http://www.astrosurf.com/jpmasviel/unpe ... comete.pdf
Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/
Re: C2014Q2
Posted: Mon Jan 19, 2015 11:30 pm
Hi all. Joan, Umberto, grazie! Olivier, thank you for Nicolas Biver document (any recommendations for comets absolute flux calibration? Perhaps not an easy task even with the photometric slit...).
Coming back to radial velocity, I try to measure the shift of sun absorption lines on comet observed spectrum, respect to their rest wavelengths (using some Fe I lines) for 13 jan observation, finding a Vrad value around 10 Km/s. Being reflected light, we should consider the Vrad between Sun and comet (~ -5.2 Km/s - from ephemeris - comet was slowly approaching the Sun) and Earth-comet Vrad (~ 14.4 Km/s moving away, eph.). Hoping the reasoning is correct and leave aside other local effects that can occur close to nucleus (what's impact?), observed Vrad should be the sum, 9.2 Km/s, a value not far from measured one.
Some of Fe I lines on comet spectrum and a G2V star rest spectrum:
Paolo
Coming back to radial velocity, I try to measure the shift of sun absorption lines on comet observed spectrum, respect to their rest wavelengths (using some Fe I lines) for 13 jan observation, finding a Vrad value around 10 Km/s. Being reflected light, we should consider the Vrad between Sun and comet (~ -5.2 Km/s - from ephemeris - comet was slowly approaching the Sun) and Earth-comet Vrad (~ 14.4 Km/s moving away, eph.). Hoping the reasoning is correct and leave aside other local effects that can occur close to nucleus (what's impact?), observed Vrad should be the sum, 9.2 Km/s, a value not far from measured one.
Some of Fe I lines on comet spectrum and a G2V star rest spectrum:
Paolo
Re: C2014Q2
Posted: Wed Jan 21, 2015 10:58 pm
Weather continues to be very bad here, so I took the opportunity to reduce an old observation (5 jan)... Just an attempt to capture CN 3880 bands with Lhires III 1200. The two bands are not individually resolved in this R~3200 spectrum:
Rigel in the same spectral interval:
Paolo
Rigel in the same spectral interval:
Paolo
Re: C2014Q2
Posted: Sat Jan 24, 2015 11:40 am
Spectrum from last night with Alpy600.
Cheers
Miguel
Cheers
Miguel
Re: C2014Q2
Posted: Sat Jan 24, 2015 6:54 pm
Bonsoir à tous
Good evening everyone
Spectres hier soir Alpy600
Spectrum from last night with Alpy600
Ce soir, météo mauvaise (un peu de repos !)
Tonight, bad weather (some rest!)
Cdt
Pierre
Good evening everyone
Spectres hier soir Alpy600
Spectrum from last night with Alpy600
- C2014q2_20150123_778_Pierre Dubreuil.png (11.17 KiB) Viewed 8250 times
Tonight, bad weather (some rest!)
Cdt
Pierre
Re: C2014Q2
Posted: Wed Jan 28, 2015 3:34 pm
Hello:
The Comet in last night.
J.Guarro.
The Comet in last night.
J.Guarro.